Total robotic liver transplant: the final frontier of minimally invasive surgery.

The use of robotic surgery in transplantation is increasing; however, robotic liver transplantation (RLT) remains a challenging undertaking. To our knowledge, this is a report of the first RLT in North America and the first RLT using a whole graft from a deceased donor in the world. This paper describes the preparation leading to the RLT and the surgical technique of the operation. The operation was performed in a 62-year-old man with hepatitis C cirrhosis and hepatocellular carcinoma with a native Model for End-Stage Liver Disease score of 10. The total console time for the operation was 8 hours 30 minutes, and the transplant hepatectomy took 3 hours 30 minutes. Warm ischemia time was 77 minutes. Biliary reconstruction was performed in a primary end-to-end fashion and took 19 minutes to complete. The patient had an uneventful recovery without early allograft dysfunction or surgical complications and continues to do well after 6-months follow-up. This paper demonstrates the feasibility of this operation in highly selected patients with chronic liver disease. Additional experience is required to fully understand the role of RLT in the future of transplant surgery. Narrated video is available at https://youtu.be/TkjDwLryd3I.

Robotic living donor nephrectomy is associated with reduced post-operative opioid use compared to hand-assisted laparoscopic approach.

BACKGROUND: Robotic donor nephrectomy (RDN) has emerged as a safe alternative to laparoscopic donor nephrectomy (LDN). Having previously demonstrated comparable efficacy, this study aims to examine postoperative analgesia use (opioid and non-opioid) in the two groups. METHODS: We conducted a retrospective review of 300 living donor nephrectomies performed at our center, comparing 150 RDN's with a contemporary cohort of 150 hand-assisted LDN's. In addition to clinical and demographic information, data on postoperative inpatient opioid and non-opioid analgesia (from patient's arrival to the surgical floor after surgery till the time of discharge) was collected. Opioid dosages were standardized by conversion to morphine milligram equivalents (MME). All patients were managed post-operatively under a standardized ERAS pathway for living donor nephrectomy patients. RESULTS: There were no significant differences in donor age, gender, and BMI between RDN and LDN groups. Total post-operative opioid use (MME's) was significantly lower in RDN patients (RDN 27.1 vs. LDN 46.3; P < 0.0001). Breakdown of opioid use with post-operative (POD) day demonstrated significantly lower use in RDN group on POD1 (RDN 8.6 vs. LDN 17.0; P < 0.05), and POD2 (RDN 3.9 vs LDN 10; P < 0.05). RDN patients had a shorter post-operative length of stay (LOS) (RDN 1.69 days vs. LDN 1.98; P = 0.0003). There were no differences between groups in non-opioid medication use, complications, and readmission rates. CONCLUSION: RDN has comparable safety to hand-assist LDN and offers additional benefits of lower postoperative opioid requirement and a shorter hospital LOS.

The association of donor hepatitis C virus infection with 3-year kidney transplant outcomes in the era of direct-acting antiviral medications.

To determine the effect of donor hepatitis C virus (HCV) infection on kidney transplant (KT) outcomes in the era of direct-acting antiviral (DAA) medications, we examined 68,087 HCV-negative KT recipients from a deceased donor between March 2015 and May 2021. A Cox regression analysis was used to estimate adjusted hazard ratios (aHRs) of KT failure, incorporating inverse probability of treatment weighting to control for patient selection to receive an HCV-positive kidney (either nucleic acid amplification test positive [NAT+, n = 2331] or antibody positive (Ab+)/NAT- [n = 1826]) based on recipient characteristics. Compared with kidney from HCV-negative donors, those from Ab+/NAT- (aHR = 0.91; 95% confidence interval [CI], 0.75-1.10) and HCV NAT+ (aHR = 0.89; 95% CI, 0.73-1.08) donors were not associated with an increased risk of KT failure over 3 years after transplant. Moreover, HCV NAT+ kidneys were associated with a higher 1-year estimated glomerular filtration (63.0 vs 61.0 mL/min/1.73 m2, P = .007) and lower risk of delayed graft function (aOR = 0.76; 95% CI, 0.68-0.84) compared with HCV-negative kidneys. Our findings suggest that donor HCV positivity is not associated with an elevated risk of graft failure. The inclusion of donor HCV status in the Kidney Donor Risk Index may no longer be appropriate in contemporary practice.

Characterizing the risk of human leukocyte antigen-incompatible living donor kidney transplantation in older recipients.

Older compatible living donor kidney transplant (CLDKT) recipients have higher mortality and death-censored graft failure (DCGF) compared to younger recipients. These risks may be amplified in older incompatible living donor kidney transplant (ILDKT) recipients who undergo desensitization and intense immunosuppression. In a 25-center cohort of ILDKT recipients transplanted between September 24, 1997, and December 15, 2016, we compared mortality, DCGF, delayed graft function (DGF), acute rejection (AR), and length of stay (LOS) between 234 older (age ≥60 years) and 1172 younger (age 18-59 years) recipients. To investigate whether the impact of age was different for ILDKT recipients compared to 17 542 CLDKT recipients, we used an interaction term to determine whether the relationship between posttransplant outcomes and transplant type (ILDKT vs CLDKT) was modified by age. Overall, older recipients had higher mortality (hazard ratio: 1.632.072.65, P < .001), lower DCGF (hazard ratio: 0.360.530.77, P = .001), and AR (odds ratio: 0.390.540.74, P < .001), and similar DGF (odds ratio: 0.461.032.33, P = .9) and LOS (incidence rate ratio: 0.880.981.10, P = 0.8) compared to younger recipients. The impact of age on mortality (interaction P = .052), DCGF (interaction P = .7), AR interaction P = .2), DGF (interaction P = .9), and LOS (interaction P = .5) were similar in ILDKT and CLDKT recipients. Age alone should not preclude eligibility for ILDKT.

The impact of a dedicated operating room team on robotic transplant program growth and fellowship training.

INTRODUCTION: Despite considerable interest in robotic surgery, successful incorporation of robotics into transplant programs has been challenging. Lack of a dedicated OR team with expertise in both robotics and transplant is felt to be a major barrier. This paper assesses the impact of a dedicated robotic transplant team (DART) on program growth and fellowship training at one of the largest robotic transplant programs in North America. METHODS: This is a single center, retrospective review of all robotic operations performed on the transplant surgery service from October 2017 to October 2022. DART was incorporated in February 2020 and included transplant first assists (RFAs), scrub technologists and circulating nurses who received robotic training. Robotic experience before and after DART was compared to assess its impact on program growth and training. RESULTS: Four hundred and two robotic cases were performed by five transplant surgeons: 63 pre-DART and 339 post-DART. 40% of cases were transplant-related and 59.5%, HPB. There was a significant increase in case volume (2.5-10.6 cases/month, p < .0001) and complexity (36.5% vs. 70.3% high complexity cases, p < .0001) post-DART. RFA case coverage increased from 17% to 95%, and participation of transplant fellows as primary surgeons increased from 17% to 95% post-DART period (both p < .05). Conversion rates (9.5% vs. 4.1%) and room turn-around-times (TAT) (58.4 vs. 40.3 min) were lower post-DART (p < .05). There were no emergent conversions, conversions in transplant patients, or robot-related complications in either group. CONCLUSION: OR teams with expertise in robotics and transplant surgery can accelerate growth of robotic transplant programs while maintaining patient safety.

Robotic donor nephrectomy: optimizing outcomes beyond the limitations of laparoscopy.

BACKGROUND: Robotic donor nephrectomy (RDN) has emerged as a safe alternate to laparoscopic donor nephrectomy (LDN), offering improved visualization, instrument dexterity and ergonomics. There is still concern about how to safely transition from LDN to RDN. METHODS: We performed a retrospective review of 150 consecutive living donor operations (75 LDN and 75 RDN) at our center, comparing the first 75 RDN's with the last 75 LDN's performed prior to the initiation of the robotic transplant program. Operative times and complications were used as surrogates of efficiency and safety, respectively, to estimate the learning curve with RDN. RESULTS: RDN was associated with a longer total operative time (RDN 182 vs LDN 144 min; P < 0.0001) but a significantly shorter post-operative length of stay (RDN 1.8 vs LDN 2.1 days; P = 0.0213). Donor complications and recipient outcomes were the same between both groups. Learning curve of RDN was estimated to be about 30 cases. CONCLUSIONS: RDN is a safe alternate to LDN with acceptable donor morbidity and no negative impact on recipient outcomes even during the early part of the RDN learning curve. Surgeon preferences for the robotic approach compared to traditional laparoscopy will require further scrutiny to improve ergonomics and operative efficiency.

The association of center volume with transplant outcomes in selected high-risk groups in kidney transplantation.

BACKGROUND: In context of increasing complexity and risk of deceased kidney donors and transplant recipients, the impact of center volume (CV) on the outcomes of high-risk kidney transplants(KT) has not been well determined. METHODS: We examined the association of CV and outcomes among 285 U.S. transplant centers from 2000-2016. High-risk KT were defined as recipient age ≥ 70 years, body mass index (BMI) ≥ 35 kg/m2, receiving kidneys from donors with kidney donor profile index(KDPI) ≥ 85%, acute kidney injury(AKI), hepatitisC + . Average annual CV for the specific-high-risk KT categorized in tertiles. Death-Censored-Graft-Loss(DCGL) and death at 3 months, 1, 5, and 10 years were compared between CV tertiles using Cox-regression models. RESULTS: Two hundred fifty thousand five hundred seventy-four KT were analyzed. Compared to high CV, recipients with BMI ≥ 35 kg/m2 had higher risk of DCGL in low CV(aHR = 1.11,95%CI = 1.03-1.19) at 10 years; recipients with age ≥ 70 years had higher risk of death in low CV(aHR = 1.07,95%CI = 1.01-14) at 10 years. There was no difference of DCGL or death in low CV for donors with KDPI ≥ 85%, hepatitisC + , or AKI. CONCLUSIONS: Recipients of high-risk KT with BMI ≥ 35 kg/m2 have higher risk of DCGL and recipients age ≥ 70 years have higher risk of death in low CV, compared to high CV. Future studies should identify care practices associated with CV that support optimal outcomes after KT.

Survival After Simultaneous Pancreas-Kidney Transplantation in Type 1 Diabetes: The Critical Role of Early Pancreas Allograft Function.

Simultaneous pancreas-kidney transplantation (SPK) carries about a 7%-22% risk of technical failure, but the impact of early pancreas allograft loss on subsequent kidney graft and patient survival is not well-defined. We examined national transplant registry data for type 1 diabetic patients who received SPK between 2000 and 2021. Associations of transplant type (i.e., SPK, deceased-donor kidney transplant [DDKA], living-donor kidney transplant [LDKA]) with kidney graft failure and patient survival were estimated by multivariable inverse probability of treatment-weighted accelerated failure-time models. Compared to SPK recipients with a functioning pancreas graft 3 months posttransplant (SPK,P+), LDKA had 18% (Time Ratio [TR] 0.82, 95%CI: 0.70-0.95) less graft survival time and 18% (TR 0.82, 95%CI: 0.68-0.97) less patient survival time, DDKA had 23% (TR 0.77, 95%CI: 0.68-0.87) less graft survival time and 29% (TR 0.71, 95%CI: 0.62-0.81) less patient survival time, and SPK with early pancreas graft loss had 34% (TR 0.66, 95%CI: 0.56-0.78) less graft survival time and 34% (TR 0.66, 95%CI: 0.55-0.79) less patient survival time. In conclusion, SPK,P+ recipients have better kidney allograft and patient survival compared with LDKA and DDKA. Early pancreas graft failure results in inferior kidney and patient survival time compared to kidney transplant alone.

Corrigendum: Survival After Simultaneous Pancreas-Kidney Transplantation in Type 1 Diabetes: The Critical Role of Early Pancreas Allograft Function.

[This corrects the article DOI: 10.3389/ti.2022.10618.].

The learning curve of deceased donor liver transplant during fellowship training.

Liver transplantation (LT) is a complex operation that most transplant surgeons learn in fellowship. Training varies as there is lack of objective data that can be used to standardize teaching. We performed a retrospective review of our adult LT database with aim of looking at fellow's experience. Using American Society of Transplant Surgery cutoff of, at least 45 LT during fellowship, data for first 45 LT were compared to LT 45-90. Fellow's cases were also clustered in sequential groups of 15 LT and analyzed to estimate the learning curve (LC). Comparison of LT 1-45 with LT 46-90 showed significantly lower total operative times (TOT) (324 vs. 344 min) and warm ischemia times (WIT) (28 vs. 31 min) in the 45-90 group. Rates of biliary complications (23.8% vs. 16.4%) and bile leaks alone (10.3% vs. 5.5%) were significantly higher for first 45 LT. Analysis of fellows experience in sequential clusters of 15 LT showed decreasing TOT, WIT, biliary complications and rates of unplanned return to the OR with progression of fellowship. This study validates the current ASTS requirement of at least 45 LT. LC generated using these data can help individualize training and optimize outcomes through identification of areas in need of improvement.

Delayed graft function and acute rejection following HLA-incompatible living donor kidney transplantation.

Incompatible living donor kidney transplant recipients (ILDKTr) have pre-existing donor-specific antibody (DSA) that, despite desensitization, may persist or reappear with resulting consequences, including delayed graft function (DGF) and acute rejection (AR). To quantify the risk of DGF and AR in ILDKT and downstream effects, we compared 1406 ILDKTr to 17 542 compatible LDKT recipients (CLDKTr) using a 25-center cohort with novel SRTR linkage. We characterized DSA strength as positive Luminex, negative flow crossmatch (PLNF); positive flow, negative cytotoxic crossmatch (PFNC); or positive cytotoxic crossmatch (PCC). DGF occurred in 3.1% of CLDKT, 3.5% of PLNF, 5.7% of PFNC, and 7.6% of PCC recipients, which translated to higher DGF for PCC recipients (aOR = 1.03 1.682.72 ). However, the impact of DGF on mortality and DCGF risk was no higher for ILDKT than CLDKT (p interaction > .1). AR developed in 8.4% of CLDKT, 18.2% of PLNF, 21.3% of PFNC, and 21.7% of PCC recipients, which translated to higher AR (aOR PLNF = 1.45 2.093.02 ; PFNC = 1.67 2.403.46 ; PCC = 1.48 2.243.37 ). Although the impact of AR on mortality was no higher for ILDKT than CLDKT (p interaction = .1), its impact on DCGF risk was less consequential for ILDKT (aHR = 1.34 1.621.95 ) than CLDKT (aHR = 1.96 2.292.67 ) (p interaction = .004). Providers should consider these risks during preoperative counseling, and strategies to mitigate them should be considered.

The demise of islet allotransplantation in the United States: A call for an urgent regulatory update.

Islet allotransplantation in the United States (US) is facing an imminent demise. Despite nearly three decades of progress in the field, an archaic regulatory framework has stymied US clinical practice. Current regulations do not reflect the state-of-the-art in clinical or technical practices. In the US, islets are considered biologic drugs and "more than minimally manipulated" human cell and tissue products (HCT/Ps). In contrast, across the world, human islets are appropriately defined as "minimally manipulated tissue" and not regulated as a drug, which has led to islet allotransplantation (allo-ITx) becoming a standard-of-care procedure for selected patients with type 1 diabetes mellitus. This regulatory distinction impedes patient access to islets for transplantation in the US. As a result only 11 patients underwent allo-ITx in the US between 2016 and 2019, and all as investigational procedures in the settings of a clinical trials. Herein, we describe the current regulations pertaining to islet transplantation in the United States. We explore the progress which has been made in the field and demonstrate why the regulatory framework must be updated to both better reflect our current clinical practice and to deal with upcoming challenges. We propose specific updates to current regulations which are required for the renaissance of ethical, safe, effective, and affordable allo-ITx in the United States.

Three-month pancreas graft function significantly influences survival following simultaneous pancreas-kidney transplantation in type 2 diabetes patients.

Successful simultaneous pancreas-kidney transplantation (SPK) improves quality-of-life and prolongs kidney allograft and patient survival in type-1 diabetic (T1DM) patients. However, the use of SPK in type-2 diabetic (T2DM) patients remains limited. We examined a national transplant registry for 35 849 T2DM kidney disease patients who received transplant between 2000 and 2016 and survived the first 3 months with a functioning kidney, and categorized as: deceased-donor kidney transplant alone (DD-KA, 68%), living-donor kidney transplant alone (LD-KA, 30%), or SPK (2%). Among SPK recipients, 6% had pancreas allograft failure within 3 months (SPK,P-) and 94% had a functional pancreas (SPK,P+). Associations of transplant type with kidney allograft failure and death (multivariable-adjusted hazard ratio, 95%LCL aHR95%UCL ), over follow-up through December 2018, were quantified by multivariable inverse probability of treatment weighted survival analyses. SPK recipients had better kidney graft and patient survival than LD-KA or DD-KA recipients. Compared to SPK,P+, DD-KA, or LD-KA recipients had significantly higher risk of kidney allograft failure (DD-KA: aHR 1.53 2.203.17 ; LD-KA: aHR 1.29 1.872.71 ) and death (DD-KA: aHR 2.12 3.255.00 ; LD-KA: aHR 1.54 2.353.59 ). SPK,P- recipients had significantly higher risk of death (aHR 1.68 3.306.50 ). Similar to T1DM, T2DM patients with SPK have a survival benefit compared to those with kidney transplant alone, but this benefit depends upon successful early pancreas function.

Variation in use of procurement biopsies and its implications for discard of deceased donor kidneys recovered for transplantation.

The use of procurement biopsies in deceased donor kidney acceptance is controversial. We analyzed Scientific Registry of Transplant Recipients data (n = 59 328 allografts, 2014-2018) to describe biopsy practices across US organ procurement organizations (OPOs) and examine relationships with discards, using hierarchical modeling to account for OPO and donor factors. Median odds ratios (MORs) provide the median of the odds that allografts with identical reported traits would be biopsied or discarded from 2 randomly drawn OPOs. Biopsies were obtained for 52.7% of kidneys. Biopsy use rose in a graded manner with kidney donor profile index (KDPI). Biopsy rates differed significantly among OPOs (22.8% to 77.5%), even after adjustment for KDPI and other donor factors. Discard rates also varied from 6.6% to 32.1% across OPOs. After adjustment for donor factors and OPO, biopsy was associated with more than 3 times the likelihood of discard (adjusted odds ratio [95%LCL aOR95%UCL ], 3.29 3.513.76 ). This association was most pronounced for low-risk (KDPI <20) kidneys (aOR, 5.45 6.477.69 ), with minimal impact at KDPI >85 (aOR, 0.88 1.151.51 ). Adjusted MORs for kidney discard and biopsy were greatest for low-risk kidneys. Reducing the rate of unnecessary biopsy and improving the accuracy of histologic assessments in higher KDPI organs may help reduce graft discard rates.

Survival Benefit with Kidney Transplants from HLA-Incompatible Live Donors.

BACKGROUND: A report from a high-volume single center indicated a survival benefit of receiving a kidney transplant from an HLA-incompatible live donor as compared with remaining on the waiting list, whether or not a kidney from a deceased donor was received. The generalizability of that finding is unclear. METHODS: In a 22-center study, we estimated the survival benefit for 1025 recipients of kidney transplants from HLA-incompatible live donors who were matched with controls who remained on the waiting list or received a transplant from a deceased donor (waiting-list-or-transplant control group) and controls who remained on the waiting list but did not receive a transplant (waiting-list-only control group). We analyzed the data with and without patients from the highest-volume center in the study. RESULTS: Recipients of kidney transplants from incompatible live donors had a higher survival rate than either control group at 1 year (95.0%, vs. 94.0% for the waiting-list-or-transplant control group and 89.6% for the waiting-list-only control group), 3 years (91.7% vs. 83.6% and 72.7%, respectively), 5 years (86.0% vs. 74.4% and 59.2%), and 8 years (76.5% vs. 62.9% and 43.9%) (P<0.001 for all comparisons with the two control groups). The survival benefit was significant at 8 years across all levels of donor-specific antibody: 89.2% for recipients of kidney transplants from incompatible live donors who had a positive Luminex assay for anti-HLA antibody but a negative flow-cytometric cross-match versus 65.0% for the waiting-list-or-transplant control group and 47.1% for the waiting-list-only control group; 76.3% for recipients with a positive flow-cytometric cross-match but a negative cytotoxic cross-match versus 63.3% and 43.0% in the two control groups, respectively; and 71.0% for recipients with a positive cytotoxic cross-match versus 61.5% and 43.7%, respectively. The findings did not change when patients from the highest-volume center were excluded. CONCLUSIONS: This multicenter study validated single-center evidence that patients who received kidney transplants from HLA-incompatible live donors had a substantial survival benefit as compared with patients who did not undergo transplantation and those who waited for transplants from deceased donors. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases.).

Hospital readmissions following HLA-incompatible live donor kidney transplantation: A multi-center study.

Thirty percent of kidney transplant recipients are readmitted in the first month posttransplantation. Those with donor-specific antibody requiring desensitization and incompatible live donor kidney transplantation (ILDKT) constitute a unique subpopulation that might be at higher readmission risk. Drawing on a 22-center cohort, 379 ILDKTs with Medicare primary insurance were matched to compatible transplant-matched controls and to waitlist-only matched controls on panel reactive antibody, age, blood group, renal replacement time, prior kidney transplantation, race, gender, diabetes, and transplant date/waitlisting date. Readmission risk was determined using multilevel, mixed-effects Poisson regression. In the first month, ILDKTs had a 1.28-fold higher readmission risk than compatible controls (95% confidence interval [CI] 1.13-1.46; P < .001). Risk peaked at 6-12 months (relative risk [RR] 1.67, 95% CI 1.49-1.87; P < .001), attenuating by 24-36 months (RR 1.24, 95% CI 1.10-1.40; P < .001). ILDKTs had a 5.86-fold higher readmission risk (95% CI 4.96-6.92; P < .001) in the first month compared to waitlist-only controls. At 12-24 (RR 0.85, 95% CI 0.77-0.95; P = .002) and 24-36 months (RR 0.74, 95% CI 0.66-0.84; P < .001), ILDKTs had a lower risk than waitlist-only controls. These findings of ILDKTs having a higher readmission risk than compatible controls, but a lower readmission risk after the first year than waitlist-only controls should be considered in regulatory/payment schemas and planning clinical care.

Development of immune response to tissue-restricted self-antigens in simultaneous kidney-pancreas transplant recipients with acute rejection.

Simultaneous kidney-pancreas transplantation (SKP Tx) is a treatment for end-stage kidney disease secondary to diabetes mellitus. We investigated the role of immune responses to donor human leukocyte antigens (HLA) and tissue-restricted kidney and pancreas self-antigens (KSAgs and PSAgs, respectively) in SKP Tx recipients (SKP TxRs). Sera collected from 39 SKP TxRs were used to determine de novo Abs specific for KSAgs (collagen-IV, Col-IV; fibronectin, FN) and PSAgs (insulin, islet cells, glutamic acid decarboxylase, and pancreas-associated protein-1) by ELISA. KSAg-specific IFN-γ, IL-17, and IL-10 cytokines were enumerated by ELISpot. Abs to donor HLA classes I and II were determined by Luminex assay. Abs to KSAgs and PSAgs were detectable in recipients with rejection compared with stable recipients (P<.05). Kidney-only rejection recipients had increased Abs against KSAgs compared with stable (P<.05), with no increase in Abs against PSAgs. Pancreas-only rejection recipients showed increased Abs against PSAgs compared to stable (P<.05), with no Abs against KSAgs. SKP TxRs with rejection showed increased frequencies of KSAg-specific IFN-γ and IL-17 with reduction in IL-10-secreting cells. SKP TxRs with rejection developed Abs to KSAgs and PSAgs demonstrated increased frequencies of kidney or pancreas SAg-specific IFN-γ and IL-17-secreting cells with reduced IL-10, suggesting loss of peripheral tolerance to SAgs.

Successful use of minimal incision superficialization technique for arteriovenous fistula maturation.

BACKGROUND: Successful cannulation is an important prerequisite for a functional arteriovenous fistula (AVF). Reasons for unsuccessful cannulation of an AVF are multifactorial and poorly evaluated. In our experience, a needle access segment (NAS) with a length of 10 cm, <5 mm deep from the skin surface, and >6 mm diameter assessed objectively using duplex Doppler ultrasound (DDUS) imaging, in a fistula with brachial artery flow >500 mL/min, permits consistent cannulation. This report provides observational data on the NAS of the outflow veins after fistula creation and a detailed long-term outcome on AVFs that needed superficialization of the NAS using minimal incision superficialization technique (MIST) to make them suitable for cannulation. This report is based on prospectively collected data with a longitudinal follow-up in a large patient cohort. METHODS: A prospective database was used to analyze consecutive patients undergoing AVF until the study end point. All patients underwent a protocol-based maturation evaluation using color DDUS imaging. Unsuitable NAS were surgically corrected using superficialization (by MIST or lipectomy) of deeply situated veins or NAS reconstruction. RESULTS: Between February 1, 2007, and May 31, 2013, 617 new AVF surgeries were performed. Outflow vein superficialization (MIST or lipectomy) or NAS reconstruction was necessary in 226 of 585 procedures (38.6%) included in this analysis. Of these, 162 (72%) were performed using MIST, 50 (22%) with a single long incision, and 14 (6%) using lipectomy technique. Technical success for MIST was 100%, and only two fistulae failed to mature. The vein depth of 9.2 ± 3.2 mm during initial vessel mapping was similar to the pre-MIST depth of 9.1 ± 3.8 mm. Depth of NAS improved to 3.1 ± 1.0 mm after MIST. The secondary patency after MIST at 6, 12, 24, 48, and 60 months was 98%, 93.3%, 88.1%, 83.3%, and 80.9%. During the 400.8 post-MIST functional fistula-years, only 0.63 procedures per year were required to maintain AVF patency. CONCLUSIONS: Our data suggest that maturation of AVFs using objective criteria based on DDUS provides an opportunity to identify NAS problems in outflow veins before cannulation. Most of the of the AVF outflow veins (71.7%) could be transposed or superficialized using MIST, with excellent long-term outcomes.